https://techcrunch.com/2018/11/07/the-cost-of-energy-storage-has-stalled-adoption-of-renewable-power-energy-vault-has-a-solution/

Since solar and wind power are now cheaper to produce than energy from fossil fuels, the only obstacle that remains to the mass adoption of renewable power is the amount of money utilities need to spend to store the energy those systems produce.

Right now, storing 100 megawatts of renewable energy (enough to power roughly 600,000 homes) means spending roughly $65.6 million on massive batteries like the kind made by Tesla, or relying on huge pumped hydro-electric storage projects that essentially create man-made dams where the release of water spins turbines to generate energy (those projects are typically far larger than 100 megawatts).